The most common riding mowers have been the tractor type which either pull a mower deck or have a deck under the belly of the mower. The great shortcoming of the tractor-type mower is its lack of maneuverability. Zero-turning-radius mowers have been developed that steer through variable forward and reverse traction which is applied to the rear driving wheels. This improved maneuverability.
Traction steering mowers generally fall into two types, either a front deck mount or a mid-deck mount. Each type has its own advantages and related problems. One of the mid-mount mowers' advantages is in its compact footprint (size). Its greatest shortcoming is the difficulty of accessing the mower deck for service and maintenance, such as cleaning dirt and debris or sharpening and/or changing blades. More specifically, an operator or service technician must raise the front end of the mower vehicle off the ground, utilizing jacks or ramps to a height sufficient for a person to crawl under the mower deck for maintenance. Some of the dangers of the above include the risk of the vehicle falling on the servicing person, getting dirt or debris in that person's eyes, and the difficulty of checking for bent blades and blade tracking while in this position. Because of these difficulties, many mid-mount mower decks do not receive thorough or timely maintenance.
Several prior art patents (see U.S. Pat. No. 6,988,351) have addressed the problems associated with deck maintenance on mid-mount mowers. In one embodiment the mower deck is unlatched at the rear and the front of the mower vehicle is raised manually allowing the deck to hinge forward from the rear. In this method, the mowers front castor wheels hang over the exposed underneath side of the mower deck blocking some of the accessibility. In other embodiments of the prior art (see U.S. Pat. No. 5,475,971) hydraulic cylinders or electric screw actuators are used to power hinge the deck forward for access. The shortcomings of all these concepts include that they must be designed into the mower and cannot be retrofitted into existing mower designs and the cost of the hydraulics and/or electric components. These costs limit their use to high-end commercial mowers and exclude their use on residential class mowers.
Existing prior art mid-mount mowers use one of two basic frame and front axle designs. One type has a rigid frame with the front castor wheels solidly attached. The other type has front castor wheels mounted to an axle that pivots on the front of the rigid frame. The rigid frame design works well on smooth ground, but rides rough on uneven ground. While mowing a slope, if the ground is rough, it is common for the up-hill front wheel to lose contact with the ground. The pivoting-axle mid-mount mower has improved some of these shortcomings but it has problems of its own. Mid-mount mowers carry the deck from flexible links fastened to the mower frame. When the front wheels encounter dips or rises on the ground surface, this cannot be translated to the mower deck because the front castor wheels are attached to an axle that is pivoting on the center of the front of the mower frame. The mowing deck follows mostly the dictates of the rear wheels that haven't as yet reached these ground conditions. This causes the mower deck to dip and cut unevenly.
The product of this is usually an uneven cut or at worst ground scalping. Because of the advantages and the associated problems of the pivoting front axle, many pivoting-axle mowers have a locking pin to convert them back to a solid frame for certain mowing conditions.